There has been long-standing concern regarding the undesirable jamming of infrared (IR) signals transmitted within consumer electronics systems. Such IR jamming occurs when two or more transmitting devices simultaneously transmit IR signals that cannot be resolved at a receiving device. A typical scenario in which IR jamming may occur involves consumer electronics systems, such as home theater systems, wherein primary and secondary IR signals are transmitted between the components of the consumer electronics system.
For example, FIG. 1 depicts a prior art consumer electronics system 10, which generally includes a remote control 12, a television 14, and an audio/video device 16, e.g., an audio receiver, video cassette recorder (VCR), etc. The remote control 12 can be used to perform a variety of operations within the consumer electronics system 10. The performance of such operations within the consumer electronics system 10 may require different transmission protocols to be used, since typically, the individual components of a consumer electronics system are fabricated by different manufacturers. These differences, however, are transparent to the remote control 12, which utilizes the television 14 to communicate with other devices, including the audio/video device 16. This arrangement, however, is susceptible to IR jamming problems.
Although a jamming problem typically does not arise when the operation is performed within the television 14, the same cannot be said when the operation is performed within the audio/video device 16, since the remote control 12 communicates with the audio/video device 16 through the television 14, creating the possibility that two signals may be transmitted to the audio/video device 16. Specifically, an operation can be performed in the audio/video device 16 by depressing a corresponding remote function key 18 on the remote control 12. In response, a primary IR signal SIR1 is transmitted to the television 14. The television 14 detects and interprets the primary IR signal SIR1, and then transmits a corresponding secondary IR signal SIR2 to the audio/video device 16, which, in the absence of IR interference, effects the performance of the operation in the audio/video device 16. If the audio/video device 16 is visible to the remote control 12, however, there is a chance that the audio/video device 16 will receive the primary IR signal SIR1 as IR interference simultaneous with the secondary IR signal SIR2. In this case, the primary IR signal SIR1 acts as a jamming signal, thereby creating a jamming problem.
This jamming problem usually occurs when the remote function key 18 (e.g., the function key that controls volume-up or volume-down) is continuously depressed, creating a high likelihood that the remote control 12 will still be transmitting the primary IR signal SIR1 during transmission of the secondary IR signal SIR2 from the television 14. In this case, the remote control 12 does not gain control of the audio/video device 16 until the remote function key 18 is released, i.e., when the audio/video device 16 no longer receives the interfering primary IR signal SIR1. Thus, this specific jamming problem creates the annoying situation where the user, anticipating that the continuous depression of the remote function key 18 will repeatedly perform the corresponding operation in the audio/video device 16, continuously depresses the remote function key 18 with no results. Only after the remote function key 18 is released is the corresponding operation performed, but only slightly. Thus, in order to repeatedly perform the operation within the audio/video device 16, the user is forced to repeatedly depress the remote function key 18, which may be an annoying task in itself.
This IR jamming phenomenon is illustrated in FIG. 2. Waveform 20 represents the continuous depression of the remote function key 18, remaining high as long as the corresponding remote function key 18 is depressed. Waveform 22 represents the primary IR signal SIR1, which is transmitted from the remote control 12 in response to the depression of corresponding the remote function key 18. As can be seen, the primary IR signal SIR1 is continuously transmitted in the form of a series of data blocks 28 for the duration that the corresponding remote function key 18 remains depressed. Waveform 24 represents the secondary IR signal SIR2, which is transmitted from the television 14 in response to the detection and interpretation of the primary IR signal SIR1. The secondary IR signal SIR2 is continuously transmitted in the form of a series of data blocks 30 for the duration that the primary IR signal SIR1 is received from the remote control 12. Waveform 26 represents the duration of the performance of the corresponding operation within the audio/video device 16, remaining low until the operation is performed. As can be seen, the operation is not performed until the transmission of the primary IR signal SIR1 terminates, signifying the release of the corresponding function key 18. At this point, the audio/video device 16 is receiving only the secondary IR signal SIR2, allowing the corresponding operation to be performed without significant IR interference. Such control is momentary, however, since the transmission of the secondary IR signal SIR2 ceases when the primary IR signal SIR1 is no longer detected.
Thus, there arises a need to prevent IR jamming in consumer electronics systems that utilize primary and secondary signals to effect the performance of an operation in response to a continuous remote function key press.